Update create_master_lists.py

as requested in :

- #219

>In GRIB2 Template definition files the octet number (from - to) for each entry in the GRIB section is given.
Most of the GRIB processing software packages need the length or number of octets for each entry, which has to be calculated from the specification of "OctetNo".
But with variables and repitition within some templates an automated calculation is sometimes not easy. (e.g. 37 + (ND-1)*4 + (NF-1)*4 -40 +(ND-1)*4 + (NF-1)*4)
Therefore, this is a proposal to add a column with the length of each entry in the GRIB2_Template files.

scripts/create_master_lists.py

@@ -68,7 +68,28 @@ def close(self):
             xmlfile.write(xml)            
 
 
+def parse_octet_length(octet_str):
+    # attempt to compute the length for simple cases
+    # fallback if expression is more complex
+    if any(sym in octet_str for sym in ['(', ')', '+', '*', 'ND', 'NF']):
+        return "Expression: " + octet_str
 
+    total_length = 0
+    parts = [p.strip() for p in octet_str.split(',')]
+    for p in parts:
+        range_match = re.match(r'^(\d+)-(\d+)$', p)
+        single_match = re.match(r'^(\d+)$', p)
+        if range_match:
+            start = int(range_match.group(1))
+            end = int(range_match.group(2))
+            total_length += (end - start + 1)
+        elif single_match:
+            total_length += 1
+        else:
+            return "Expression: " + octet_str
+    return str(total_length)
+
+
 def process_files(files,pattern,writers,title_prefix):
 
     rows=[]
@@ -141,6 +162,13 @@ def process_files(files,pattern,writers,title_prefix):
     rows = [row for *_,row in decorated]
 
 
+
+    # For Template rows, add computed Length
+    if pattern == 'GRIB2_Template':
+        for row in rows:
+            octet_str = row.get("OctetNo", "")
+            row["Length"] = parse_octet_length(octet_str)
+
     for row in rows:
         for writer in writers:
             writer.write_row(row)            
@@ -176,13 +204,12 @@ def process_files(files,pattern,writers,title_prefix):
     # Template tables
     template_files = load_files("GRIB2_Template",basedir=".")
 
-    fieldnames=["Title_en","OctetNo","Contents_en","Note_en","noteIDs","codeTable","flagTable","Status"]    
+    #  Added "Length" to both fieldnames and xml_elements
+    fieldnames=["Title_en","OctetNo","Contents_en","Note_en","noteIDs","codeTable","flagTable","Length","Status"]
     csv_writer = CSVWriter("txt/Template.txt",fieldnames)
 
-    xml_elements=["Title_en","OctetNo","Contents_en","Note_en","noteIDs","codeTable","flagTable","Status"]
+    xml_elements=["Title_en","OctetNo","Contents_en","Note_en","noteIDs","codeTable","flagTable","Length","Status"]
     xml_writer = XMLWriter("xml/Template.xml",xml_elements,"GRIB2_Template_en")
 
     writers = [csv_writer,xml_writer]
     process_files(template_files,"GRIB2_Template",writers,"Identification template")
-
-